After a few days and nights of clouds and some much needed rain, the skies cleared up over Tucson and San Diego. But last night still was hampered by less than great weather. In Tucson, clouds were a problem for the first few hours of the night and then fog formed during the last couple of hours. In San Diego, clouds were also an occasional problem.

Two minor showers have become active during the past few nights. Neither shower is expected to produce more than 2-3 meteors per hour at their peak.

The December Monocerotids (sometimes just called the Monocerotids) are produced by Comet C/1917 F1 (Mellish). Discovered in 1917 this bright comet is on a ~145 year orbit and isn’t due back till around 2062. There is evidence that this shower may have produced a number of bright fireballs during the 11th through 16th century. The shower is predicted to peak on December 7th-9th with a paltry 2 meteors per hour radiating from the faint constellation of Monoceros (located just east of Orion).

The December Phoenicids (also just called the Phoenicids) radiate from the far southern constellation of Phoenix. Due to its southern radiant, this shower is very difficult to observe from the Northern Hemisphere. The shower results from the break-up or splitting of Comet P/1819 W1 (Blanpain) in 1819. Most years the shower only produces a few meteors per hour but on occasion up to 100 meteors per hour have been seen (1887, 1938 and 1956). No further outbursts are predicted until 2050 though that doesn’t mean we can’t be surprised. The shower is predicted to peak on December 6. Note, that though the Phoenicids are very difficult to see from the Northern Hemisphere, Bob’s San Diego camera picked one up last night.

Scientists from the University of Calgary have successfully found a number of meteorites from the spectacular fireball seen over western Canada on November 20th. The meteorites were found strewn over a many kilometer-wide area near the city of Lloydminster along the borders of Alberta and Saskatchewan. This spot is very close to the predicted fall area based on eyewitness reports and videos of the fireball.

Though the analysis is still preliminary, and might even be considered hearsay at this point, the meteorites appear to be a type of Ordinary Chondrite (OC). OCs are the most common type of meteorites seen to fall to Earth and are related to S-type asteroids. Though S-type asteroids are not the most common type of asteroid in space they are the dominant type in the inner half of the asteroid Main Belt between Mars and Jupiter. It is from this region of the asteroid Main Belt that the majority of the asteroids and meteoroids that cross the Earth’s orbit (and hence can impact the Earth) come from.

When the small asteroid that caused the fireball was traveling through space it was a single chunk of rock. Early estimates put its size and mass at up to a few meters across and up to 10 tons. During its quick trip through the Earth’s atmosphere, atmospheric and thermal (heat) forces broke the asteroid up into hundreds or thousands of pieces. Though much of its mass completely burnt up, enough of the remaining pieces survived to hit the ground to be found as meteorites.It is possible that there are thousands of meteorites to be found from this fireball.

Over the next few weeks or months analysis of the fireball’s orbit and the composition of the meteorites will be published. I will post further updates as more info is released.

It rained all of last night here in Tucson so there are no meteor observations to report.

Though this is not related to the usual meteors, comets and asteroids that are the focus of this blog, the coolest show in the sky right now are the planets Venus and Jupiter. Both planets can be seen in the evening right after it gets dark. In fact, these two are the brightest “stars” in the sky.

Both planets are located low in the southwest sky. Venus is the brighter “star” and is currently lower in the sky than Jupiter. Over the next few evenings, watch as Jupiter appears to “fall” towards Venus. On December 1st, the planets will be closest together (~2 degrees or 4 Moon diameters). That evening a slim crescent Moon will also be located very close to the pair. Some parts of the world will be able to watch as the Moon passes directly between the 2 planets. In western Europe, the Moon will appear to pass in front of (or occult) Venus. For North American observers, the Moon will have already passed by the 2 planets (but still be located very close to them) on the evening of the 1st.

After the 1st, Jupiter will continue to start each evening lower in the sky until it is finally too close to the Sun to be seen

Last night didn’t start great with thick clouds over Tucson. It didn’t end well either since I woke up to light sprinkles. The nice thing about our camera set-up is that it can run all night long, rain or shine (“moonshine?”). For a few hours last night it was clear enough for the camera to detect 16 meteors which isn’t a bad haul for this time of the year.

You will notice a few changes in the meteor showers being monitored. For the first time since late September the Taurids are no longer being searched for. Rather we have once again begun searching for Antihelion meteors. For a summary of what the Antihelions are, see the post “Sept 12/13th and Antihelion meteors“.

Obs Date (UT) TotTime TOT SPO ANT
TUS 2008-11-26 06h 00m 16 16 0

TUS – Camera in Tucson operated by Carl Hergenrother
SDG – Camera in San Diego operated by Bob Lunsford
TotTime – Total amount of time each camera looked for meteors
TOT – Total number of meteors detected
SPO – Sporadics (meteors not affiliated with any particular meteor shower)
ANT – Antihelions

Clouds were a problem all night long in Tucson. As a result, only 3 meteors were seen.

One of the meteors was a very nice, bright Southern Taurid that crossed almost the entire camera field of view (~60 degrees). What makes this meteor even more impressive is the fact that it was observed through thick cirrus. In the video below only one star is visible. [Even though there are 3 bright “stars” visible in the upper right part of the frame, the two “stars” closest to the right edge are not stars but “hot pixels”. “Hot pixels” are detector pixels that are brighter than normal.] The only actual star is Deneb, the brightest star in the constellation Cygnus.

This is just a quick update on the spectacular fireball seen over Western Canada on evening of November 20.

According to Alan Hildebrand of the University of Calgary, and an expert on meteors and meteorites, the asteroid that caused the fireball had a mass between 1 and 10 tons and may have been as large as a small desk. Objects of this size usually fragment into many smaller pieces while traveling through the atmosphere. Many of these, much smaller, pieces may have survived to hit the ground. If they did, the meteorites will be spread over many hundreds of square miles (or kilometers). Dr. Hildebrand has determined the most likely area to find the meteorites is around Manitou Lake near the town of Macklin, Saskatchewan, about 100 kilometers south of Lloydminster, near the Alberta boundary.

I have received a few sighting of this fireball from observers located throughout the United States and Canada. As can be seen from the map above, this particular fireball was only observed from Alberta, Saskatchewan and Montana. During any one night there are many fireballs seen around the world, though most will be fainter than the Canadian one.

According to the AMS Fireball Sightings Log, at least 5 additional fireballs as bright or brighter than the Moon were observed. Quite a few of these have been reported in the comments section of this blog.

The nicest fireball story in the Transient Sky comments section was written by Daisy Moreau about the AL/MS/AR/LA/TX fireball:

“On November 20, 2008, my two grandson and I were watching their helium filled balloon fly away in Alexandria, La.. The time was 5:35 p.m.and the most beautiful comet flew across the sky. It was a bright blue with green and a fire tail of red, orange and yellow. It took out breath away. My youngest grandson Hayden said, “Oh, look, someone is shooting fireworks”. Not believing my eyes, I asked the older grandson, Garrett, “What color was that?”, He said all the primary colors. We have tried to draw and color it but nothing we drew could even come close to the beauty in the sky. When Hayden let his balloon go, we said it was going up to heaven to my mother, their great grandmother, then when we saw the comet we just knew in our hearts that my Mother threw us a star.”

The video and links are carried over from my original posting on the Canadian fireball.

Last night turned out to be a rather good night for observing from both Tucson and San Diego. But not a great night since some cirrus was around. With a strong Pacific storm forecast to swing through CA and AZ, the rest of the week may not be conducive for meteor observing from San Diego and Tucson.

From Bob Lunsford’s notes: “The weather was actually clear most of the night, much to my surprise. There was occasional cirrus and the humidity was very high, limiting the transparency of the sky. This is very good for planetary observers but not for meteor observations.

This may be the last night of observing for awhile as storms are forecast to arrive tomorrow and over the weekend.”

The Leonids are now officially over and have been dropped from the table below. The 17 meteors seen by the Tucson camera is the lowest nightly tally (for a night with little or no clouds) since Oct 12th.